Function themeModeForBackgroundColor

src/core/themeDetection.ts:68–75

({ red, green, blue }: RgbColor)

/** Classify a background color using relative luminance. */
export function themeModeForBackgroundColor({ red, green, blue }: RgbColor): TerminalThemeMode {
  const linear = [red, green, blue].map((component) => {
    const normalized = component / 255;
    return normalized <= 0.03928 ? normalized / 12.92 : ((normalized + 0.055) / 1.055) ** 2.4;
  });
  const luminance = 0.2126 * linear[0]! + 0.7152 * linear[1]! + 0.0722 * linear[2]!;
  return luminance > 0.5 ? "light" : "dark";
}

/**
 * Probe the terminal background via OSC 11 using the same input stream OpenTUI uses for mouse.